Santos Silva told Members of Parliament a few hours before the vote at the British parliament that Brexit was "bad news," and that an exit without an agreement would be "catastrophic news."

He said if the UK asks for a deadline extension, it would imply a unanimous position of member states, including Portugal.

Santos Silva added that if the UK decides to reverse Brexit, that would not cause "any problem for Portugal."

The agreement between London and Brussels implies a transition period until December 2020, but the possibility of it being voted down after two years of upheaval is considerable.

The document being voted down could force the British government to ask for an extension for the negotiation period stipulated by Article 50 of the Lisbon Treaty, which ends on 29 March.

There is also a possibility, validated by the European Court of Justice, of the British government revoking unilaterally the request to exit the EU.

Santos Silva highlighted that the agreement currently on the table was the "best agreement possible" taking into account "contradictions" in Britain's stance such as wanting the free movement of people and maintaining the movement of goods, services and capital.